This invention is directed to an electronic wristwatch including an auxiliary power supply for energizing the wristwatch when the main power supply is removed for replacement, and in particular to an electronic wristwatch including an auxiliary battery for energizing the timekeeping circuit in an electronic wristwatch in order to insure that the timekeeping information stored therein is not lost when the main battery utilized to energize the wristwatch is removed therefrom in order to replace same.
Electronic wristwatches, and in particular those utilizing a quartz crystal vibrator as a high frequency time standard, have undergone rapid and remarkable technological improvements in the last few years. These improvements have taken into account the timekeeping accuracy of electronic wristwatches, the performance of numerous additional functions such as chronographic operation, calculator operation, etc., and improved assembly techniques leading to more reliable and more highly miniaturized wristwatches. With respect to the accuracy of such electronic wristwatches, it is noted that electronic wristwatches having an accuracy of ten seconds per month have become commonplace, and in fact, timepieces that are accurate to one second a month or three seconds per year have been commercialized. Such highly accurate wristwatches require little if any correction or adjustment unless the DC battery, utilized to energize same, is replaced. Moreover, each time that a battery is replaced, the timekeeping information stored in the timekeeping circuitry volatilizes, thereby rendering it necessary to reset the timekeeping circuit after a new battery is exchanged for a dead battery. Thus, when a new battery is exchanged for an old battery, an external time reference, such as a radio or telephone indication of correct time, must be utilized to correct and adjust the timepiece, a feature which makes electronic wristwatches unacceptable to many consumers.
Similarly, in wristwatches that perform a plurality of functions, in particular digital display wristwatches of the type that operate in a chronographic mode and/or in a calculator mode, a memory is utilized to process the additional functional information. In addition to the hours, minutes and seconds timekeeping information, the type of information and operations such as measuring the month, day, day of the week, year, leap year, elapsed time (stopwatch), world time and alarm signaling are volatilized when the battery is removed from the timepiece. Moreover, all of this information, in a multi-functional timepiece, must once again be restored in the respective counters and registers once the battery is replaced thereby making it necessary for the battery to be replaced by a watchmaker or other person having particular expertise with respect to the information and operations noted above.
Moreover, certain of the different functions performed by a multi-functional timepiece, such as alarm signaling, increase the drain on the battery, thereby requiring the battery to be replaced more often. The more often the battery is replaced, the greater the disadvantages noted above become. Although the size of the battery can be increased, the trend in electronic wristwatch design is toward miniaturization of the timepiece and, in particular, a reduction in the thickness thereof, thereby ruling out increasing the size of the battery in order to reduce the frequency with which same must be replaced. Accordingly, an electronic wristwatch wherein information stored by the timepiece circuitry is not volatilized when the battery is removed from the wristwatch for replacement is desired.